Posted by: Mike Clark
Thanks for the comments.
The Model H hasnít much room for a feedwater heater inside the gas flue so I have been thinking of making a muffler size heat exchanger to go underneath the flue. So as to make this short and shallow (it would be about 24 inches long by 5 wide by 2 deep, extending from the position of the exhaust manifold to just in front of the rear axle) I thought up the idea shown on this link. [photos1.flickr.com
I might also insulate the outside of the case.
Steam would be directed up and down through the 3 loops of pipe by a pair of corrugated sheets placed above and below the pipe loops so as to trap and hold them in place. This should be much more effective than just letting the steam pass along the length of the loops.
I can get about 12 feet of pipe in - my question is would this be enough to be of use and secondly would it be better to go for 3/8 pipe instead of 5/16ths so the water remains exposed to the heat for longer (the surface/volume ratio would be less but the actual surface area would be greater).